Master website event sale seats availability psa tde

- Task: https://www.odoo.com/web?#id=9971&view_type=form&model=project.task&menu_id=3942&action=327
- Pad: https://pad.odoo.com/p/r.BTJ9yFYnbxBG3VzQ
`existing_registrations` is a recordset and the `write` doesn't depend on the current record, so why the iteration instead of just
```python
if confirm:
    existing_registrations.write({'state': 'open'})
```
?